Just an update to document the process. Both MIs doing well, eating everything but pellets so far. Feeding heavy and needing a 50% water change, although the SPS are looking good and clams are fuller than usual. Still getting along as a pair, going to push that and see how long I can manage them together. I think as long as I provide surplus food, they may get along.
Interesting note, a friend bought 2 others from the same shipment, lost them both one week in. I don't have a lot of detail on his tank, so can't venture a real guess, but both were eating well from the second day.
I'm feeling like dissolved O2 has a big role in their survival, and if you've got a heavy photosynthetic load and run a night mode on pumps, I think the chances of waking up to dead fish goes way up. I have huge surface agitation in my tank, so hoping that's the secret. Time will tell...